1. Field of the Invention
The invention relates to a friction roller in a conveyor. More particularly, the invention relates to a friction roller in a conveyor which conveys an object in an assembly line.
2. Description of the Related Art
Japanese Patent Laid-Open Publication No. JP-A-8-207843 discloses an example of a conveyor which conveys an upper automobile body to a welding process in an automobile body assembly line. In this case, a conveyor 31 includes a long frame 32, and multiple friction rollers 33 fitted to a lateral portion of the frame 32 in a longitudinal direction, as shown in FIG. 13. Each of the friction rollers 33 is driven to rotate when a rotation shaft 35 is rotated by a gear mechanism 36 connected to a drive shaft of a motor 34. A jig pallet 37 on which an upper automobile body B is placed is conveyed on the friction rollers 33. According to the Japanese Patent Laid-Open Publication No. JP-A-8-207843, the assembly line is configured such that welding is performed by a welding machine when the automobile body B is conveyed on the conveyor 31 (refer to FIG. 1 and FIG. 2).
The inner peripheral face of the friction roller 33 is rotated when the rotation shaft 35 is rotated by the motor 34, whereby the jig pallet 37 is conveyed.
Also, in another conveyor line, a jig pallet 2 on which an upper automobile body B is placed includes one long rail 3, as shown in FIG. 1. When a friction roller 40 which is in contact with a lateral face portion of the rail 3 is rotated, the rail 3 itself is moved along a proceeding direction, and the automobile body B placed on the rail 3 can be conveyed.
As shown in FIG. 14, in the friction roller 40, an elastic ring 42 is integrally joined, using an adhesive or the like, to an outer peripheral face of a support roller 41 which has a drive shaft fitting hole 41a. When the elastic ring 42 which is in contact with the rail 3 is driven to rotate by the motor, the rail is conveyed through friction.
In addition, other examples of a conventional conveyance roller used in a conveyor or the like are disclosed in Japanese Patent Laid-Open Publication No. JP-A-2001-206528 (refer to FIG. 1), Japanese Utility Model Laid-Open Publication No. JP-A-6-83622 (refer to FIG. 1), Japanese Patent Laid-Open Publication No. JP-A-2000-351438 (refer to FIG. 1), and the like.
However, in the friction roller 40 shown in FIG. 14, the elastic ring 42 is made of urethane rubber. Since the rail 3 of the heavy jig pallet 2 is conveyed by frictional force of the elastic ring 42 which is rotated, the elastic ring 42 itself greatly wears out, and accordingly the friction roller 40 is frequently replaced with a new one.
Since the elastic ring 42 is integrated with the support roller 41 using an adhesive or the like, it is not possible to easily replace only the worn out elastic ring 42 with a new one when replacing the friction roller 40 with a new one. Therefore, the elastic ring 42 is discarded together with the support roller 41. Alternatively, the elastic ring 42 is peeled from the support roller 41 and a new elastic ring 42 is rejoined to the support roller 41 using an adhesive in order to suppress an increase in cost. As a result, cost increases or workability decreases.
The conveyance roller disclosed in the Japanese Patent Laid-Open Publication No. JP-A-2001-206528 is formed by externally fitting an external cylinder to a roller main body. The external cylinder is formed by joining an elastic plate to a cylindrical body using an adhesive. Therefore, when the elastic plate wears out, the external cylinder itself including the cylindrical body is replaced with a new one. In other words, as described above, since peeling the joined elastic plate from the cylindrical body results in a decrease in workability, the external cylinder itself needs to be replaced with a new one, which increases the cost. Also, when the external cylinder is externally fitted to the roller main body, the external cylinder needs to be prevented from dropping off the roller main body using an engagement ring, which results in an increase in cost and a decrease in workability.
A roller disclosed in the Japanese Utility Model Laid-Open Publication No. JP-A-6-83622 is suitably used as a roller for a conveyor for conveying powders or grains which apply a small load. In this case, an elastic ring is directly fitted to a roller or a pulley which is rotated without using the support roller 41, unlike the friction roller 40 shown in FIG. 14. Therefore, the load that the elastic ring receives is small. Accordingly, it is not suitable to use the roller as the friction roller for a conveyor for conveying, for example, an automobile body which applies a large load, since the roller would greatly wear out due to the large load.
In the case of a roller disclosed in the Japanese Patent Laid-Open Publication No. JP-A-2000-351438, an elastic member is fixed to a metallic fitting member by insert molding. Therefore, when the elastic member wears out, the elastic member needs to be discarded together with the metallic fitting member, which results in an increase in cost.